/**
 * Copyright 2015-现在 广州市领课网络科技有限公司
 */
package com.roncoo.education.common.core.tools;

import lombok.extern.slf4j.Slf4j;
import org.springframework.util.StringUtils;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.sql.Timestamp;
import java.util.UUID;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicLong;

/**
 * <p>
 * 高效GUID产生算法(sequence),基于Snowflake实现64位自增ID算法。 <br>
 * 优化开源项目 http://git.oschina.net/yu120/sequence
 * </p>
 *
 * @author hubin
 * @Date 2016-08-01
 */
@Slf4j
public class IdWorker {

    /**
     * 主机和进程的机器码
     */
    private static final Sequence worker = new Sequence();

    public static long getId() {
        return worker.nextId();
    }

    /**
     * <p>
     * 获取去掉"-" UUID
     * </p>
     */
    public static synchronized String get32UUID() {
        return UUID.randomUUID().toString().replace("-", "");
    }

    static class Sequence {

        /* 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动） */
        private final long twepoch = 1288834974657L;
        private final long workerIdBits = 5L;/* 机器标识位数 */
        private final long datacenterIdBits = 5L;
        private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
        private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
        private final long sequenceBits = 12L;/* 毫秒内自增位 */
        private final long workerIdShift = sequenceBits;
        private final long datacenterIdShift = sequenceBits + workerIdBits;
        /* 时间戳左移动位 */
        private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
        private final long sequenceMask = -1L ^ (-1L << sequenceBits);

        private long workerId;

        /* 数据标识id部分 */
        private long datacenterId;
        private long sequence = 0L;/* 0，并发控制 */
        private long lastTimestamp = -1L;/* 上次生产id时间戳 */

        public Sequence() {
            this.datacenterId = getDatacenterId(maxDatacenterId);
            this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
        }

        /**
         * @param workerId     工作机器ID
         * @param datacenterId 序列号
         */
        public Sequence(long workerId, long datacenterId) {
            if (workerId > maxWorkerId || workerId < 0) {
                throw new RuntimeException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
            }
            if (datacenterId > maxDatacenterId || datacenterId < 0) {
                throw new RuntimeException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
            }
            this.workerId = workerId;
            this.datacenterId = datacenterId;
        }

        /**
         * <p>
         * 获取 maxWorkerId
         * </p>
         */
        protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
            StringBuilder mpid = new StringBuilder();
            mpid.append(datacenterId);
            String name = ManagementFactory.getRuntimeMXBean().getName();
            if (StringUtils.hasText(name)) {
                /*
                 * GET jvmPid
                 */
                mpid.append(name.split("@")[0]);
            }
            /*
             * MAC + PID 的 hashcode 获取16个低位
             */
            return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
        }

        /**
         * <p>
         * 数据标识id部分
         * </p>
         */
        protected static long getDatacenterId(long maxDatacenterId) {
            long id = 0L;
            try {
                InetAddress ip = InetAddress.getLocalHost();
                NetworkInterface network = NetworkInterface.getByInetAddress(ip);
                if (network == null) {
                    id = 1L;
                } else {
                    byte[] mac = network.getHardwareAddress();
                    if (null != mac) {
                        id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
                        id = id % (maxDatacenterId + 1);
                    }
                }
            } catch (Exception e) {
                log.error(" getDatacenterId: " + e.getMessage());
            }
            return id;
        }

        /**
         * 获取下一个ID
         *
         * @return
         */
        public synchronized long nextId() {
            long timestamp = timeGen();
            if (timestamp < lastTimestamp) {// 闰秒
                long offset = lastTimestamp - timestamp;
                if (offset <= 5) {
                    try {
                        wait(offset << 1);
                        timestamp = timeGen();
                        if (timestamp < lastTimestamp) {
                            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
                        }
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                } else {
                    throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
                }
            }

            if (lastTimestamp == timestamp) {
                // 相同毫秒内，序列号自增
                sequence = (sequence + 1) & sequenceMask;
                if (sequence == 0) {
                    // 同一毫秒的序列数已经达到最大
                    timestamp = tilNextMillis(lastTimestamp);
                }
            } else {
                // 不同毫秒内，序列号置为 1 - 3 随机数
                sequence = ThreadLocalRandom.current().nextLong(1, 3);
            }

            lastTimestamp = timestamp;

            return ((timestamp - twepoch) << timestampLeftShift) // 时间戳部分
                    | (datacenterId << datacenterIdShift) // 数据中心部分
                    | (workerId << workerIdShift) // 机器标识部分
                    | sequence; // 序列号部分
        }

        protected long tilNextMillis(long lastTimestamp) {
            long timestamp = timeGen();
            while (timestamp <= lastTimestamp) {
                timestamp = timeGen();
            }
            return timestamp;
        }

        protected long timeGen() {
            return SystemClock.now();
        }

    }

    static  class SystemClock {

        private final long period;
        private final AtomicLong now;

        private SystemClock(long period) {
            this.period = period;
            this.now = new AtomicLong(System.currentTimeMillis());
            scheduleClockUpdating();
        }

        private static SystemClock instance() {
            return InstanceHolder.INSTANCE;
        }

        public static long now() {
            return instance().currentTimeMillis();
        }

        public static String nowDate() {
            return new Timestamp(instance().currentTimeMillis()).toString();
        }

        private void scheduleClockUpdating() {
            ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(new ThreadFactory() {
                @Override
                public Thread newThread(Runnable runnable) {
                    Thread thread = new Thread(runnable, "System Clock");
                    thread.setDaemon(true);
                    return thread;
                }
            });
            scheduler.scheduleAtFixedRate(new Runnable() {
                @Override
                public void run() {
                    now.set(System.currentTimeMillis());
                }
            }, period, period, TimeUnit.MILLISECONDS);
        }

        private long currentTimeMillis() {
            return now.get();
        }

        private static class InstanceHolder {
            public static final SystemClock INSTANCE = new SystemClock(1);
        }

    }
}

